Gaseous fuel injector

ABSTRACT

An injector for gaseous fuel, the injector comprising a body provided with a fuel feed duct and with a fuel delivery duct, the fuel feed duct and the fuel delivery duct opening out into a chamber of the body in which there are mounted a valve member and an actuator means for actuating the valve member between a closed position and an open position in which the valve member defines a fuel flow section, wherein the fuel delivery duct comprises a calibrated segment of section smaller than the flow section defined by the valve member when in the open position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of application PCT/FRO3/02419,filed Jul. 30, 2003, and claims priority to French patent application 0209664 filed Jul. 30, 2002, the disclosures of which are incorporatedherein by reference in their entirety.

FIELD

The present invention relates to a fuel injector. The fuel injector maybe used with gaseous fuel. The fuel injector may be suitable for use insingle- or dual-carburetion engines running on liquefied petroleum gas(LPG) or the like.

In this application, the injector may serve to introduce gaseous fuel ata determined flow rate into a combustion chamber of the engine.

BACKGROUND

An injector for gaseous fuel generally comprises a body provided with afuel feed duct, and with a fuel delivery duct for delivering fuel fromthe injector. The fuel feed duct and the fuel delivery duct eachgenerally has a first end opening out to the outside of the body forconnection to the fuel tank and the combustion chamber of the engine,respectively, and a second end opening out into a chamber of the bodyhaving mounted therein a valve member and means for actuating the valvemember between a closed position in which the valve member is pressedagainst the second end of the fuel delivery duct, and an open positionin which the valve member is spaced apart from the second end of thefuel delivery duct in order to define a fuel flow section. This fuelflow section is generally cylindrical in shape and of area equal to theproduct of the circumference of the second end of the fuel delivery ductmultiplied by the distance between the second end of the fuel deliveryduct and the valve member when in the open position. This distancecorresponds to the stroke of the valve member. The fuel flow section asdefined in this way defines the flow rate with which fuel is deliveredto the combustion chamber, and must therefore be precise since itinfluences the performance of the engine.

Unfortunately, the stroke of the valve member depends on the dimensionsof the valve member itself and of certain components of the actuatormeans, and also on the clearances that exist between these variouselements. The accuracy of the stroke thus depends on the quality of themachining and on the quality of the assembly of the various elements,thus making manufacture of the injector difficult. In addition, theeffects of temperature, shocks, vibration, and general wear all lead tochanges (which are only temporary for temperature) to the dimensions andthe clearances defining the stroke, such that the fuel flow section andthe delivery flow rate do not remain constant over time. Thus, there isa need to have an injector capable of delivering fuel without unexpectedvariations in the delivery flow rate.

SUMMARY

One embodiment is directed to an injector for gaseous fuel, the injectorcomprising a body comprising a fuel feed duct and a fuel delivery duct,the fuel feed duct and the delivery duct opening out into a chamber ofthe body in which there are mounted a valve member, and an actuatormeans for actuating the valve member between a closed position and anopen position in which the valve member defines a fuel flow section,wherein the fuel delivery duct comprises a calibrated segment of sectionsmaller than the fuel flow section defined by the valve member when inthe open position. The section of the calibrated segment determines thedelivery flow rate independent of the stroke of the valve member.

This embodiment may provide an injector capable of delivering fuelwithout unexpected variations in flow rate.

Other characteristics and advantages of the invention appear on readingthe following description of a particular and non-limiting embodiment ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic section view of an injector in accordance withone embodiment, the valve member being in its closed position.

FIG. 2 is a fragmentary diagrammatic view in section of an injector, thevalve member being in its open position.

DETAILED DESCRIPTION

With reference to FIG. 1 and FIG. 2, the injector in accordance with anembodiment comprises a body 1 comprised of a top half-body 2 and abottom half-body 3 that are fastened to one another.

The top half-body 2 and the bottom half-body 3 define between them achamber into which there opens out a fuel feed duct 5 and a fueldelivery duct 6.

The fuel feed duct 5 is formed in the bottom half-body 3 and has a firstend that opens to the outside of the body 1 for connection to the fueltank of a motor vehicle, and a second end that opens out into thechamber 4.

The fuel delivery duct 6 is formed in an endpiece 7 mounted on thebottom half-body 3 so that the fuel delivery duct 6 has a first end thatopens to the outside the body 1 for connection to the combustion chamberof an engine, and a second end that opens out via an opening 8 into thechamber 4.

The fuel delivery duct 6 has a frustoconical segment 9 extending fromthe opening 8 to a calibrated segment 10, tapering towards thecalibrated segment 10, followed by a terminal segment 11 which isconnected to the calibrated segment 10.

The frustoconical segment 9 has an angle of less than 55° at the angleof the frustoconical segment 9. The frustoconical segment 9 could havean angle of any suitable number of degrees at its apex, including, butnot limited to substantially equal to 40°. A suitable number of degreesfor the angle at the apex of the frustoconical segment is one thatlimits disturbances of flow rate in the frustoconical segment 9.

The calibrated segment 10 comprises a section which is designed tocorrespond to the delivery rate that is to be supplied by the injector.The terminal segment 11 is of section that is not less than that of thecalibrated segment 10.

The fuel delivery duct 6 is also arranged to ensure that the flow speedof the fuel in the calibrated segment 10 is sonic. In this way, adelivery flow rate is obtained that is substantially constant in spiteof variations in the pressure downstream from the calibrated segment 10.

The chamber 4 is subdivided into a top compartment 12 and a bottomcompartment 13, wherein the top compartment 12 is located above thebottom compartment 13. The chamber 4 is subdivided into the topcompartment 12 and the bottom compartment 13 by means of a diaphragm 14which extends transversely to the axis of the fuel delivery duct 6 atthe opening 8. The diaphragm 14 comprises a peripheral edge 15 heldcaptive between the top half-body 2 and the bottom half-body 3, acentral portion in register with the opening 8 in order to form a valvemember 16, and an intermediate portion 17 connecting the peripheral edge15 to the central portion 16. The intermediate portion 17 is elasticallydeformable so that the valve member 16 of the diaphragm 14 can movebetween a closed position (as illustrated in FIG. 1) in which the valvemember 16 is pressed against the edge of the opening 8, and an openposition (as illustrated in FIG. 2), in which the valve number 16 isspaced apart from the edge of the opening 8 and cooperates therewith todefine a fuel flow section for the fuel. The fuel flow section can beany number of suitable shapes, including, but not limited to,cylindrical. The area of cylindrical fuel flow section can be equal tothe product of the circumference of the opening 8 multiplied by thedistance between the edge of the opening 8 and the valve number in thediaphragm 14. The circumference of the opening 8 and the distancebetween the edge of the opening 8 and the in the diaphragm 14 can bedesigned so that a cylindrical fuel flow section is greater than thesection of the calibrated segment 10 so that the delivery rate isdetermined by the section of the calibrated segment 10 and not by thecylindrical fuel flow section.

The injector has means for actuating the valve member 16 in thediaphragm 14 to move between the open and closed positions of the valvemember. These actuator means can be housed in the top compartment 12 ofthe chamber 4 and comprise a magnetic core 18 surrounded by a coil 19associated with means providing a connection with an electrical powersupply 20 (not shown). In order to improve return of the valve member 16in the diaphragm 14 to the closed position of the valve member 16, afraction of the fuel taken from the fuel feed duct 5 can be deliveredinto the top compartment 12 in order to establish a backing pressuretherein. By way of example, and not be way of limitation, for an opening8 comprised of a diameter of 8 millimeters (mm) and a diaphragm having acentral portion 16 with a stroke of 0.3 mm, the calibrated segment 10can have a diameter of about 2 mm.

Naturally, the invention is not limited to the embodiment described andvariants can be applied thereto without going beyond the ambit of theinvention as defined by the claims. The structure of the injector may bedifferent from that described, and for example the bottom half-body 3and the endpiece 7 may be constructed to be a single part. The actuatormeans may also be different and could, for example, incorporatemechanical means for returning the valve member 16 into its closedposition. For example, the mechanical means can include, but is notlimited to, a spring. The numerical values mentioned are given purely byway of example.

1. An injector for gaseous fuel, the injector comprising: a body comprising: a chamber of the body in which there is mounted a valve member and an actuator means for actuating the valve member between a closed position and an open position in which the valve member defines a fuel flow section a fuel feed duct; and a fuel delivery duct, wherein the fuel feed duct and the fuel delivery duct open out into a chamber of the body, wherein the fuel delivery duct comprises includes a calibrated segment of section smaller than the fuel flow section defined by the valve member when the valve member is in the open position.
 2. An injector according to claim 1, wherein the fuel delivery duct comprises a frustoconical segment extending from the chamber to the calibrated section, tapering towards the calibrated section.
 3. An injector according to claim 2, wherein the frustoconical segment has an angle at the apex of the frustoconical segment of less than about 55°.
 4. An injector according to claim 1, wherein the fuel delivery duct is arranged to obtain a flow speed of fuel in the calibrated segment that is substantially sonic.
 5. An injector according to claim 2 wherein the frustoconical segment has an angle at the apex of substantially 40°.
 6. An injector according to claim 1, comprising: a bottom half-body; and an end piece mounted on the bottom half-body.
 7. An injector according to claim 1, comprising a single part which comprises both a bottom half-body and an end piece.
 8. An injector according to claim 1, wherein the actuator means comprises mechanical means.
 9. An injector according to claim 8, wherein the mechanical means comprises a spring.
 10. A fuel injector, the injector comprising: a body comprising: a chamber in which there is mounted, a valve member, and an actuator for actuating the valve member between a closed position and an open position, the valve member defining a fuel flow section when it is in the open position; a fuel feed duct; and a fuel delivery duct, the fuel delivery duct opening into the chamber; wherein the fuel delivery duct comprises a calibrated segment of section smaller than the fuel flow section which is defined by the valve member when the valve member is in the open position.
 11. An injector according to claim 10, wherein the fuel delivery duct is arranged to obtain a flow speed of fuel in the calibrated segment that is substantially sonic.
 12. An injector according to claim 10, wherein the fuel delivery duct includes a frustoconical segment extending from the chamber to the calibrated section, tapering towards the calibrated section.
 13. An injector according to claim 10 wherein the frustoconical segment has an angle at the apex of less than about 55°.
 14. An injector according to claim 10 wherein the frustoconical segment has an angle at the apex of substantially 40°.
 15. An injector according to claim 10 comprising: a bottom half-body; and an end piece mounted on the bottom half-body.
 16. An injector according to claim 10 comprising a single part which comprises both a bottom half-body and an end piece.
 17. An injector according to claim 10 wherein the actuator comprises a spring.
 18. A fuel injector, comprising: a body; a valve associated with the body and having an open position, the valve member defining a fuel flow section when it is in the open position; and a fuel delivery duct, the fuel delivery duct opening into the chamber and comprising a calibrated segment of section smaller than the fuel flow section.
 19. A fuel injector, comprising: a body; and means for delivering fuel without unexpected variations in flow rate.
 20. The injector of claim 19, wherein the body comprises a chamber; the injector further comprises a means for defining a fuel flow section, the means for defining a fuel flow section being arranged in the body; and the means for delivering fuel without unexpected variations in flow rate comprises a means for delivering fuel to the chamber, the means for delivering fuel to the chamber being associated with the means for defining a fuel flow section.
 21. The injector of claim 20, wherein the means for delivering fuel to the chamber comprises a frustoconical segment. 